The present invention relates to a module with embedded electronic components and, more particularly, to a module having a plurality of embedded electronic components which are mounted on a substrate and encapsulated in a resin.
Electronic devices such as a mobile telephone and a mobile music reproducer have been increasingly reduced in size and weight under the slogan of “miniaturization”. Consequently, it is essential for components used for electronic devices to be also reduced in size and weight and the development thereof has been promoted toward further miniaturization. As part of the development, the development of a module product (semiconductor device) in which a semiconductor integrated circuit and components such as a resistor and a capacitor are collectively mounted on a single substrate to perform a specified function can be mentioned.
As such a module product, a module in which a semiconductor chip and chip components such as a chip capacitor and a chip resistor are mounted on a substrate to perform a battery protecting function or the like has been known. Examples of the module are disclosed in, e.g., Japanese Laid-Open Patent Publication Nos. 2002-190564, 2002-190565, 2002-190486, 2005-109135, and 2002-208668. It has been common practice to entirely encapsulate such a module in a resin for the purpose of protecting the semiconductor chip and chip components mounted thereon.
Such a module product is soldered by a reflow process onto a mounting substrate such as a printed wiring substrate. However, as described in Japanese Laid-Open Patent Publication No. 2002-208668, the problem has been encountered that the solder of a soldered component (chip component) remelts in the module during a reflow-mounting step, which leads to the occurrence of a short circuit. According to Japanese Laid-Open Patent Publication No. 2002-208668, the short-circuit phenomenon occurs as follows. When the solder remelts, it undergoes melt expansion and produces a pressure (remelt expansion pressure) which causes delamination at the interface between the component and a resin or at the interface between the resin and the module substrate. As a result, the solder flushingly flows in the delaminated portion and provides an undesirable linkage between the both-end terminals of the chip component, which results in the short-circuit phenomenon. To prevent the phenomenon, Japanese Laid-Open Patent Publication No. 2002-208668 discloses the use of a resin which has both the ability (mechanical strength) to protect internal components and flexibility capable of reducing the remelt expansion pressure of the solder.
However, the resin disclosed in Japanese Laid-Open Patent Publication No. 2002-208668 is a special resin. Before using the special resin in place of a conventional encapsulating resin, there are numerous requirements to be satisfied, including ease of molding, a satisfactory yield after encapsulation, and long-term in-use stability. In addition, there is also the problem of higher cost.